Re: [PATCH] device-dax: don't set kobj parent during cdev init

From	Dan Williams <dan.j.williams@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] device-dax: don't set kobj parent during cdev init
Date	2017-02-11 20:00 +0100
Message-ID	<t9L3Q-4eF-19@gated-at.bofh.it> (permalink)
References	(5 earlier) <t9BHb-6XG-17@gated-at.bofh.it> <t9K7M-3EI-13@gated-at.bofh.it> <t9KAO-441-15@gated-at.bofh.it> <t9KU9-4aS-9@gated-at.bofh.it> <t9L3Q-4eF-21@gated-at.bofh.it>
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On Sat, Feb 11, 2017 at 10:55 AM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Sat, Feb 11, 2017 at 10:43 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
>>
>> On 11/02/17 11:27 AM, Dan Williams wrote:
>>> Why, when the lifetime of the cdev is already correct?
>>
>> Well, it's only correct if you use the kobj parent trick which Greg is
>> arguing against. As someone reviewing/copying code that trick is
>> unclear, undocumented and it looks rather odd messing with internal
>> kobjects. Taking the explicit reference would be very clear, very
>> standard and only net one additional line.
>>
>>> See commit ba09c01d2fa8 "dax: convert to the cdev api". I used to take
>>> explicit references like you suggest, but cdev made it cleaner.
>>
>> I agree that, on the whole, that patch makes things a good deal cleaner.
>> I'm not so sure that this one small aspect is an improvement.
>>
>> In any case, it's up to you. If you'd like I can certainly submit a v2
>> patch that adds the get/put.
>
> Can we meet in the middle and just add some comments about what is going on?
>
> It's a shame to add reference counts for something that is already
> properly reference counted.

Also when using an embedded cdev how would you recommend avoiding this problem?

https://lists.01.org/pipermail/linux-nvdimm/2016-August/006562.html

Thread

[PATCH] device-dax: don't set kobj parent during cdev init Logan Gunthorpe <logang@deltatee.com> - 2017-02-10 20:20 +0100
  Re: [PATCH] device-dax: don't set kobj parent during cdev init Logan Gunthorpe <logang@deltatee.com> - 2017-02-10 20:30 +0100
  Re: [PATCH] device-dax: don't set kobj parent during cdev init Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-10 20:50 +0100
  Re: [PATCH] device-dax: don't set kobj parent during cdev init Dan Williams <dan.j.williams@intel.com> - 2017-02-10 20:50 +0100
    Re: [PATCH] device-dax: don't set kobj parent during cdev init Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-10 21:20 +0100
      Re: [PATCH] device-dax: don't set kobj parent during cdev init Dan Williams <dan.j.williams@intel.com> - 2017-02-10 23:30 +0100
        Re: [PATCH] device-dax: don't set kobj parent during cdev init Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-11 08:20 +0100
          Re: [PATCH] device-dax: don't set kobj parent during cdev init Dan Williams <dan.j.williams@intel.com> - 2017-02-11 10:00 +0100
            Re: [PATCH] device-dax: don't set kobj parent during cdev init Logan Gunthorpe <logang@deltatee.com> - 2017-02-11 19:00 +0100
              Re: [PATCH] device-dax: don't set kobj parent during cdev init Dan Williams <dan.j.williams@intel.com> - 2017-02-11 19:30 +0100
                Re: [PATCH] device-dax: don't set kobj parent during cdev init Logan Gunthorpe <logang@deltatee.com> - 2017-02-11 19:50 +0100
                Re: [PATCH] device-dax: don't set kobj parent during cdev init Dan Williams <dan.j.williams@intel.com> - 2017-02-11 20:00 +0100
                Re: [PATCH] device-dax: don't set kobj parent during cdev init Logan Gunthorpe <logang@deltatee.com> - 2017-02-12 06:50 +0100
                Re: [PATCH] device-dax: don't set kobj parent during cdev init Dan Williams <dan.j.williams@intel.com> - 2017-02-11 20:00 +0100

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